Date Difference Calculator
Count the days, weeks and months between any two dates.
Whether you're counting down to an event, working out a project timeline, or checking how long ago something happened, this calculator measures the gap between two dates. Pick a start date and an end date and it instantly shows the difference in days, weeks, and months. The order doesn't matter — it always reports the absolute distance between them. Everything runs in your browser.
How the difference is measured
The calculator finds the exact time between the two dates and converts it into three units:
Days = total gap • Weeks = days ÷ 7 • Months = days ÷ 30.44
Days are the precise count between the dates. Weeks are shown as whole weeks, and months use an average month length of about 30.44 days — the year divided by twelve — so a 90-day gap reads as roughly 3.0 months. Because months vary from 28 to 31 days, the month figure is a smooth average rather than a calendar-by-calendar count, which keeps it consistent for any pair of dates.
When to use which figure
The day count is the one to trust for anything precise — contract terms, shipping windows, or counting down to a deadline. Weeks are handy for planning schedules that run in seven-day cycles, like sprints or pay periods. The month figure is best treated as an approximation for a quick sense of scale; if you need exact calendar months and days between two dates, an age-style breakdown that borrows across real month lengths will be more precise than a simple average.
Frequently Asked Questions
Does the order of the dates matter?
No. The calculator reports the absolute difference, so swapping the start and end dates gives the same result.
Why is the month figure a decimal?
Because it uses an average month length of about 30.44 days. That keeps the result consistent for any two dates rather than jumping around with the different lengths of calendar months.
Does it include both the start and end day?
It measures the span between the two dates. If you need to count both endpoints inclusively — for example billing days — add one to the day figure.
Is anything I enter saved?
No. The calculation runs in your browser and nothing is uploaded or stored.